Gen V E92 ECM Failure?
09-29-2019, 07:05 PM
#1
Gen V E92 ECM Failure? Hoping someone might have some history or ideas. Situation as follows - 2015 Silverado with genV 5.3L L83. Recently completed AFM/DOD delete, Texas Speed stage 1 cam and custom tune by Mailordertune.com. Truck ran great for several weeks. Went into reduced power mode. Scanned the codes. There are several tied to the fuel rail pressure sensor (P018D, P0191, P0641, P06DA). Was able to track down a diagnostic procedure online. Walked through the steps to check the fuel rail pressure sensor and circuit. Found the 5v reference signal at the sensor connector putting out 7v. I am thinking OK, must be a short to voltage somewhere along this wire between sensor and ECM. To confirm, I puled the connector at the ECM - voltage drops to zero (ignition on). I double check that I had the right wire at the ECM by checking resistance at the sensor and ECM ends. Yep, correct wire. Unpulled from ECM zero volts. Plugged in - 7v. Hmm. Pulled the ECM connector off again. Checked the voltage coming out of the ECM for this 5v reference signal. Its putting out close to 9v.
So logic is now telling me the ECM must have failed internally. And somehow close to battery voltage is being pushed out the rail sensor reference signal line. But how common is a gen V ECM failure? Is it so uncommon that I should be rethinking this before buying a replacement from the dealer? I did take the time to completely unwrap the ECM wire harnesses at their connectors and about 18inches down the harness. Separated all of the wires one by one while watching the voltmeter. Not even a budge on the voltmeter as I worked through all of the wires. So I am convinced there is no short/bare wires at the ECM end of the harness. I do recall us having to lift the trans quite a bit during the engine removal & install. There is a branch of the engine harness that runs along the top drivers side of the trans. Wondering if a wire got pinched up against the body weld seam just rear of the bellhousing.
Initially I was thinking we possibly crushed a fuel injector wire when prying the rails out of the heads. Those things were crazy stuck. I tried to be careful to not pinch the injector harness between the prybar and fuel rail. But it is possible. If I am not mistaken the injector operate at higher (12v?) voltage, not 5v - correct? I was thinking maybe there is some short between an injector harness and the rail, letting some stray voltage get to the rail pressure sensor. But if that is the case, then why 9v coming out of the ECM?
One other item. It does seem the situation grew worse over a day or so. Initially when it went into reduced power mode it would at least start and run. Now with the ECM seeing 7v at the sensor, it shuts down the fuel pump (higher voltage is higher pressure) because it thinks there is enough/too much pressure. So with in this state the truck will not even run.
Any other thoughts? What would cause the 5v reference signal to be 7v, or at the ECM output pin 9v?
Thanks.
So logic is now telling me the ECM must have failed internally. And somehow close to battery voltage is being pushed out the rail sensor reference signal line. But how common is a gen V ECM failure? Is it so uncommon that I should be rethinking this before buying a replacement from the dealer? I did take the time to completely unwrap the ECM wire harnesses at their connectors and about 18inches down the harness. Separated all of the wires one by one while watching the voltmeter. Not even a budge on the voltmeter as I worked through all of the wires. So I am convinced there is no short/bare wires at the ECM end of the harness. I do recall us having to lift the trans quite a bit during the engine removal & install. There is a branch of the engine harness that runs along the top drivers side of the trans. Wondering if a wire got pinched up against the body weld seam just rear of the bellhousing.
Initially I was thinking we possibly crushed a fuel injector wire when prying the rails out of the heads. Those things were crazy stuck. I tried to be careful to not pinch the injector harness between the prybar and fuel rail. But it is possible. If I am not mistaken the injector operate at higher (12v?) voltage, not 5v - correct? I was thinking maybe there is some short between an injector harness and the rail, letting some stray voltage get to the rail pressure sensor. But if that is the case, then why 9v coming out of the ECM?
One other item. It does seem the situation grew worse over a day or so. Initially when it went into reduced power mode it would at least start and run. Now with the ECM seeing 7v at the sensor, it shuts down the fuel pump (higher voltage is higher pressure) because it thinks there is enough/too much pressure. So with in this state the truck will not even run.
Any other thoughts? What would cause the 5v reference signal to be 7v, or at the ECM output pin 9v?
Thanks.
09-30-2019, 12:04 PM
#3
Not sure which way to turn with this truck. I need it back on the road. I pulled the trigger on a new ECM, complete engine wire harness and new left & right injector harnesses. Local deal will flash the new ECM for $100. Should have everything except the engine harness within a day. The engine harness is likely delayed due to the GM strike.
10-05-2019, 07:43 PM
#4
Update on this issue. Installed the left & right fuel rail harnesses. No change. Installed the new ECM (dealer flashed it for me). No change. Installed a new fuel rail pressure sensor. No change. Still reads over 7v on the reference signal for the fuel rail pressure sensor. Dealer confirmed the same via the Tech2. So clearly the reference signal is getting 'extra' voltage from a short somewhere in the system. But where?
I started with the starter solenoid. It is triggered with 12v. Worked backwards from the starter up through the wire loom, moving/twisting the wires to see if I could get the 7v on the reference signal to fluctuate. Nothing.
The, by accident, I brushed up against the connector at the front timing cover. The connector that feeds the cam position, VVT solenoid, and oil pump. Presto - got back down to 4.95v. A little detective work and I found the oil pump is fed with a 12v signal (to the variable volume solenoid). Not sure why this solenoid requires 12v to operate, but it does. Removed the wire harness from the timing cover, which is not an easy task. It is zip-tied and taped to a metal stamping that routes it around the front of the timing cover and keeps it out of the harms way from the serpentine belt. Untaped all of the wires. I could not find any obvious shorts, cut insulation or pinching. But I taped up the 12v wire separately. Then retaped all of the wires back to the metal stamping. Reinstalled everything and problem is now solved. Several test drives with no issue. Still not sure where the cross-connection was between the 12v wire and the 5v reference wire/circuit, but everything is back to normal. And lucky for me the engine wiring harness I had on order was put on hold because of the GM strike. So I will be cancelling the order and getting my $350 back.
I started with the starter solenoid. It is triggered with 12v. Worked backwards from the starter up through the wire loom, moving/twisting the wires to see if I could get the 7v on the reference signal to fluctuate. Nothing.
The, by accident, I brushed up against the connector at the front timing cover. The connector that feeds the cam position, VVT solenoid, and oil pump. Presto - got back down to 4.95v. A little detective work and I found the oil pump is fed with a 12v signal (to the variable volume solenoid). Not sure why this solenoid requires 12v to operate, but it does. Removed the wire harness from the timing cover, which is not an easy task. It is zip-tied and taped to a metal stamping that routes it around the front of the timing cover and keeps it out of the harms way from the serpentine belt. Untaped all of the wires. I could not find any obvious shorts, cut insulation or pinching. But I taped up the 12v wire separately. Then retaped all of the wires back to the metal stamping. Reinstalled everything and problem is now solved. Several test drives with no issue. Still not sure where the cross-connection was between the 12v wire and the 5v reference wire/circuit, but everything is back to normal. And lucky for me the engine wiring harness I had on order was put on hold because of the GM strike. So I will be cancelling the order and getting my $350 back.
10-09-2019, 05:37 AM
#5
One more last (?) update on this issue. Issue came back again (high/over voltage on 5v ref signal - back into reduced power mode & shut down/no start). More digging. Found that I could turn the issue 'on/off' by moving the wires at the connector that connects the engine harness to the front/timing cover sub-harness. Hmmm, getting closer. Figured maybe we broke something internally on that connector when we were wrestling the engine out or back in. Pulled the connector apart (removed the white plastic connector separator/insulator on the female (engine harness) side of the connector. This connector faces upward when installed. Found it had coolant inside the connector. Just enough coolant that it was evident it was arching and conducting between the 7 wires in this connector. This connector contains the 5v ref signal (for the cam position sensor) and wires for the VVT cam phaser and 12v supply & signal wire for the oil pump volume solenoid. So I was getting random 12v signal bleed onto the 5v reference signal.
Connector cleaned up and reassembled. Been a few days now. No more problem!
Connector cleaned up and reassembled. Been a few days now. No more problem!
10-12-2019, 10:35 AM
#6
9 Second Club
OEM loom or aftermarket ?
You would expect all actuators to be powered from 12v. Sensors as you say are usually 5v.
Being direct injection Gen 5 ? typically these injectors operate at a fairly high voltage, not simply 12v. And certainly with piezo type injectors, they require power to both open and close, so never unplug these on a running engine if that's what they use.
You would expect all actuators to be powered from 12v. Sensors as you say are usually 5v.
Being direct injection Gen 5 ? typically these injectors operate at a fairly high voltage, not simply 12v. And certainly with piezo type injectors, they require power to both open and close, so never unplug these on a running engine if that's what they use.